As a disk drive, for example, a magnetic disk drive comprises a magnetic disk disposed in a case, spindle motor which supports and rotates the magnetic disk, a magnetic head which reads information from and writes information into the magnetic disk, and a carriage assembly which supports the magnetic head movably relative to the magnetic disk. The magnetic head has a slider attached to a suspension, and a head portion provided in the slider. The head portion comprises a recording head and a reproducing head.
Recently, a perpendicular magnetic recording magnetic head has been suggested for higher recording density, higher capacity, or a smaller size of a magnetic disk drive. In such a magnetic head, the recording head has a main magnetic pole which generates a perpendicular magnetic field, a trailing shield located on the trailing side of the main magnetic pole across a write gap to close a magnetic path between this trailing shield and the magnetic path, and a coil for passing a magnetic flux through the main magnetic pole. A high-frequency assist head has been suggested. In this high-frequency assist head, a high-frequency oscillator is provided between a medium-side end of a trailing shield and a main magnetic pole, and a current is passed to the high-frequency oscillator through the main magnetic pole and the trailing shield.
In the high-frequency assist recording head, the high-frequency oscillator is located between the main magnetic pole and the trailing shield which is located on the trailing side of the main magnetic pole, that is, the high-frequency oscillator is located on the trailing side of the main magnetic pole. A drive current is passed through this high-frequency oscillator, and the magnetization of an oscillating layer is oscillated. As a result, a great high-frequency magnetic field can be generated. Recording ability is improved in a region where the high-frequency magnetic field is superposed on a recording magnetic field coming from the main magnetic pole, and stable recording characteristics are obtained.
Increased intensity of high-frequency magnetic field is required for enhanced high-frequency recording. In this case, the high-frequency magnetic field generated on the trailing side of the main magnetic pole is also increased, and recorded bits may be reversed in the region where the high-frequency magnetic field is superposed on an effective magnetic field coming from the trailing-side end.